This disclosure relates to an impingement cooling device for a gas turbine engine that increases cooling air flow to a transition duct.
Primary components of a gas turbine engine include a compressor section, a combustion section, and a turbine section. As known, air compressed in the compressor section is mixed with fuel and burned in the combustion section to produce hot gases that are expanded in the turbine section.
A combustor is positioned at a compressor discharge opening and is connected to the turbine section by transition ducts. The transition ducts are circumferentially spaced apart from each other in an annular pattern. Each transition duct is spaced from an adjacent transition duct by a small gap. The transition ducts conduct the hot gases from the combustor to a first stage inlet of the turbine section. A cooling impingement sleeve is positioned to surround each of the transition ducts. Each impingement sleeve includes a plurality of air holes that direct cooling air toward the heated transition ducts.
Air from the compressor section exits a diffuser via a discharge casing that surrounds the transition ducts. Some of this air is directed to cool the transition duct via the air holes in the impingement sleeve. The remaining air is eventually mixed with fuel in a combustion chamber.
Due to the tight packaging constraints between the various engine components, it may be difficult to direct a sufficient amount of cooling air to the transition duct. The compressor discharge air passing between the closely spaced transition ducts is accelerated through the gap between adjacent transition ducts, which results in a low local static pressure. This reduces the pressure drop that drives cooling air through the impingement sleeve, which can result in inadequate local cooling.
One proposed solution for increasing cooling air flow has been to weld scoops onto the impingement cooling sleeve. The scoops comprise semi-hemispherical members, i.e. a curved member that forms half of a hemisphere, that are welded to the impingement cooling sleeve at different air hole locations. These scoops have not been efficient in capturing and redirecting flow through impingement cooling holes.
Accordingly, there is a need to provide an impingement sleeve configuration with a more effective cooling structure.